The present invention relates to an image processing apparatus for forming mask data which is used for image synthesis or color adjustment from image data and, more particularly, to a distributed image processing apparatus for efficiently forming mask data by a distributed process of a server client system or the like.
In recent years, due to the realization of a high integration degree of memory devices and a high speed of a processor and the appearance of devices having advanced functions such as display having a high resolution, plotter having a high resolution, color print, and the like, various editing processes such as synthesis, color conversion, and the like of color image data are being realized as a desk-top publishing (DTP) for enabling image data stored in a data base to be processed as a target by a single workstation or personal computer. In this case, the formation of mask data which is used to extract an object in the image edition causes a problem. That is, in the editing work of an image, various mask data for extraction which are matched with the image are necessary. In the formation of the mask data, the precision, high processing speed, and easiness of the formation by the operator become subjects.
FIG. 1 shows a distributed process to produce mask data which is executed for a conventional server client system as a target. A workstation 210 serving as a processing machine is connected to a server unit 212 through a local area network (LAN) 216. The server unit 212 manages a data base 214 in which actual image data has been stored. The workstation 210 comprises: a mask data processing section 218 which is realized by a processor; an internal memory 220; a mouse 222; a keyboard 224; a frame memory 226; and a color display 228.
Hitherto, mask data is produced as follows. When the operator of the workstation 210 requests a transfer of image data as a processing target to the server unit 212, the server unit 212 selects and reads out real image data from the data base 214 and transfers. In this instance, in order to directly transfer the real image data from the server unit 212, an internal memory on the workstation has to be set to a large capacity, so that the system costs increase. It also takes a long time to transfer the image data and the system performance also deteriorates. Further, as compared with a resolution of the real image data, a resolution of the color display 228 of the workstation 210 is generally low. Even when the real image data is transmitted, an image can be displayed at only a low resolution, so that the real image data becomes in vain. From those reasons, in the server unit 212, the thin-out image data obtained by thinning out the real image data is transferred to the workstation 210. When receiving the thin-out image data transferred, the workstation 210 executes a process to form mask data that is necessary by the mask data processing section 218 with respect to the thin-out image data stored in the internal memory 220 as a target. The forming process of the mask data is executed by a manual operation such that the outline of the object is designated one pixel by one with respect to the image displayed on the display 228 as a target. Since a burden on the operator is large, however, there is also realized an algorithm for searching an outline and automatically forming mask data by a difference calculus using a difference change of boundary pixels, a color mixing method using a color mixture ratio from an object color to a background color in a boundary portion, or the like. When the mask data can be formed in the workstation 210, it is sent to the server unit 212 and stored into the data base 214.
There are, however, the following problems in the conventional mask pattern forming process using such a thin-out image data. The extraction of the object image using the mask data in the image synthesis or color adjustment is executed by the server unit 212 for the real image data as a target in order to obtain a high precision. The mask data that is used for extraction of the mask data, however, is the data formed from the thin-out image data. There is a deviation between the real image data and the object outline and a problem of the extracting precision occurs. To solve such a problem, a method whereby an interpolating process is subjected to the mask data and, after that, it is used for extraction of the real image data is also considered. The errors are, however, not always perfectly eliminated by the interpolation. Therefore, in order to make it possible to perform the extraction at a high precision using the mask data, it cannot help sending the real image data to the workstation and forming the mask data. Consequently, the memory size increases, it takes a long time to load and transfer the image data, the costs in case of executing the distributed process increase, and the system performance deteriorates.